The present invention relates generally to devices for heating solids. The solids being heated are heat exchange bodies such as metallic or ceramic balls or pebbles, which are preferably used in rotating retorts for heating and crushing materials which are being processed. More specifically, the present invention relates to an improved apparatus and method for feeding the heat exchange bodies to the solids heater device.
Solid heat exchange bodies, referred to hereinafter as solids, are used in the pyrolytic processing of oil shale and other solid carbonaceous materials. The solids are utilized to heat the carbonaceous material (e.g. oil shale) by exchanging their heat to the material being processed by means of intimate contact therewith. After the carbonaceous materials are heated to the desired temperature, the solids are separated from the carbonaceous material and returned to a device which reheats the solid heat carrying bodies. Examples of such solids heating devices are disclosed in U.S. Pat. Nos. 3,595,540 and 4,193,760. These solids heating devices are commonly referred to as solids heaters or ball heaters.
Solids heaters generally include a heater shell which defines a heating chamber having a bottom, sides and a top. A flow of hot flue gas is introduced through the top of the heater shell to heat solids which are concurrently introduced into the heating chamber. The solids are introduced into the heating chamber through feed conduits which pass through the heater shell top.
After the solids are reheated to desired temperatures, various disengager and separation means are provided for separating the heated solids from the concurrently flowing flue gas. The separated or disengaged reheated solids are then passed back to the retort or other process vessel where heating of carbonaceous material is desired.
Due to the high temperatures necessary to provide desired reheating of solids, problems have been experienced with overheating or failure of various solids heater components. For example, solids heaters typically include a plurality of solids feed pipes or feed pipes or feed conduits arranged at spaced locations around the heater shell top for feeding solids to the heating chamber. The feed pipes include an inlet portion on the outside of the heater shell and an outlet portion disposed inside the heater shell within the heating chamber. The feed pipes are typically made of relatively expensive temperature resistant alloy steels. The feed pipes are welded to the heater shell top or roof in order to secure them into place. Since heater shells are typically made from carbon steel, the welding of these different types of materials to each other require special techniques that are very expensive. In addition, problems are presented in that stress at the weld joints due to different coefficients of expansion of the materials results in stress development and possible fracture at the weld locations during heating and cooling of the solids heater.
A further problem experienced with solids feed pipes is the intermittent blockage and interruption of solids flow through the feed pipe. During prolonged operation of solids heaters, partial or total blockage of the feed pipes may occur. Also, blockages and process disruptions in other portions of the solids circuit may cause the flow of solids through the feed pipes to be interrupted. When the feed pipes become blocked and when the flow of solids through the feed pipes is interrupted, the feed pipes may be subjected to overheating. This results in possible warpage and partial melting of the feed pipe.
It would therefore be desirable to provide a method and apparatus wherein the feed pipe or conduit is connected to the heater shell by some means other then welding. It is further desirable that the feed pipe be easily and quickly removed for cleaning and removal of solids blockages when plugging occurs and further be provided with means for protecting the pipes from overheating due to partial or total blockage or other solids flow interruptions.